This invention generally concerns improvements made to equipment installations configured for transporting containers, in particular bottles or similar objects, between a beginning-of-line machine which feeds the containers and an end-of-line machine which uses them. The installation may, for example, be a bottle filling unit, in which the beginning-of-line machine is a machine which manufactures containers, such as plastic bottles, and the end-of-line machine fills the bottles. The invention is also applicable to other unit configurations, such as a filling machine and a packing machine, a machine for cleaning recycled bottles and a filling machine, etc.
When the end-of-line machine is fed directly with containers arriving from the beginning-of-line machine, the stoppage of one of the machines necessarily entails the stoppage of the other machine, and, in general, of the entire equipment line. A stoppage of this type is particularly disadvantageous because of the losses of production, of energy, of raw materials, and, more generally, of money thus engendered, even though the machines other than the one stopped remain in operating condition. These disadvantages are even more pronounced in the case of some machines, such as machines which manufacture bottles from plastic material, for which the stoppage-and-restart process entails a loss of usable bottles discarded as waste, and the restart process is lengthy. Complete stoppage of this kind of machine must, therefore, be avoided at all costs.
To remedy this problem, conventional practice provides a buffer unit in a conveyor line, e.g., between a plastic bottle manufacturing machine and a filling machine, to regulate the flow of containers being transported between the beginning-of-line machine and the end-of-line machine, so that a brief stoppage of either of the two machines does not require the stoppage of the other machine, whether beginning-of-line or end-of-line.
The buffer function is widely implemented by making the conveyor chain between the beginning-of-line and end-of-line machines very long (this length can reach one hundred meters in some installations). This configuration proves very disadvantageous, since it requires a large space for the layout of the conveyor chain. To save space on the floor, this chain may, conventionally, be driven upwardly above the rest of the installation; however, the resulting complexity of the conveyor chain may entail increased cost. Furthermore, the use of a very long conveyor chain in a space of limited dimensions makes it necessary to give the chain a shape in which it is folded over on itself, with numerous curves and bends. A number of conveyor systems function properly in a straight line, but give inferior performance when the pathway is curved. The improvement of the curved operating configuration leads to greater complexity, and thereby, here again, to more costly equipment. Moreover, whatever the operating principle, the cost per linear meter of a conveyor chain is high, and any increased length is economically undesirable. In addition, transport over great lengths has the disadvantage of increasing the risk of scoring or damaging the containers.
The buffer function can also be implemented by providing shunt sections connected to the principal conveyors by means of switches. Here again, this kind of configuration requires a large available space, and its upwardly extending construction exhibits the same disadvantages as in the preceding case. Furthermore, the switches are very expensive devices which exist in great number within the unit.
Finally, conventional practice encompasses still other buffer devices formed by hoppers in which the containers are stored in bulk. These devices have the disadvantage of damaging the containers during storage and when they are extracted from the hoppers.